docs: def change_color(self, selections, value):
          '''Change the color of each atom by a certain value. *value*
          should be a tuple.
  
          '''
          if 'atoms' in selections:
              atms = selections['atoms'].mask
              if value is None:
                  #self.radii_state.array[atms] = [vdw_radii.get(t) * 0.3  for t in self.system.type_array[atms]]
                  self.atom_colors.array[atms, 0:3] = [self.color_scheme.get(t, colors.deep_pink)[0:3]
                                                       for t in self.system.type_array[atms]]
              else:
                  self.atom_colors.array[atms, 0:3] = value[0:3]
      
          self.atom_renderer.update_colors(self.atom_colors.array)
          self.on_atom_colors_changed()